gh-89263: Add typing.get_overloads

Doc/library/typing.rst

@@ -2407,6 +2407,35 @@ Functions and decorators
 
  See :pep:`484` for details and comparison with other typing semantics.
 
+ .. versionchanged:: 3.11
+ Overloaded functions can now be introspected at runtime using
+ :func:`get_overloads`.
+
+
+.. function:: get_overloads(func)
+
+ Return a sequence of :func:`@overload <overload>`-decorated definitions for
+ *func*. *func* is the function object for the implementation of the
+ overloaded function. For example, given the definition of ``process`` in
+ the documentation for :func:`@overload <overload>`,
+ ``get_overloads(process)`` will return a sequence of three function objects
+ for the three defined overloads. If called on a function with no overloads,
+ ``get_overloads`` returns an empty sequence.
+
+ ``get_overloads`` can be used for introspecting an overloaded function at
+ runtime.
+
+ .. versionadded:: 3.11
+
+
+.. function:: clear_overloads()
+
+ Clear all registered overloads in the internal registry. This can be used
+ to reclaim the memory used by the registry.
+
+ .. versionadded:: 3.11
+
+
 .. decorator:: final
 
  A decorator to indicate to type checkers that the decorated method

Lib/test/test_typing.py

@@ -1,15 +1,18 @@
 import contextlib
 import collections
+from collections import defaultdict
 from functools import lru_cache
 import inspect
 import pickle
 import re
 import sys
 import warnings
 from unittest import TestCase, main, skipUnless, skip
+from unittest.mock import patch
 from copy import copy, deepcopy
 
 from typing import Any, NoReturn, Never, assert_never
+from typing import overload, get_overloads, clear_overloads
 from typing import TypeVar, TypeVarTuple, Unpack, AnyStr
 from typing import T, KT, VT # Not in __all__.
 from typing import Union, Optional, Literal
@@ -3890,11 +3893,22 @@ def test_or(self):
  self.assertEqual("x" | X, Union["x", X])
 
 
+@lru_cache()
+def cached_func(x, y):
+ return 3 * x + y
+
+
+class MethodHolder:
+ @classmethod
+ def clsmethod(cls): ...
+ @staticmethod
+ def stmethod(): ...
+ def method(self): ...
+
+
 class OverloadTests(BaseTestCase):
 
  def test_overload_fails(self):
- from typing import overload
-
  with self.assertRaises(RuntimeError):
 
  @overload
@@ -3904,8 +3918,6 @@ def blah():
  blah()
 
  def test_overload_succeeds(self):
- from typing import overload
-
  @overload
  def blah():
  pass
@@ -3915,6 +3927,58 @@ def blah():
 
  blah()
 
+ def set_up_overloads(self):
+ def blah():
+ pass
+
+ overload1 = blah
+ overload(blah)
+
+ def blah():
+ pass
+
+ overload2 = blah
+ overload(blah)
+
+ def blah():
+ pass
+
+ return blah, [overload1, overload2]
+
+ # Make sure we don't clear the global overload registry
+ @patch("typing._overload_registry",
+ defaultdict(lambda: defaultdict(dict)))
+ def test_overload_registry(self):
+ # The registry starts out empty
+ self.assertEqual(typing._overload_registry,{})
+
+ impl, overloads = self.set_up_overloads()
+ self.assertNotEqual(typing._overload_registry,{})
+ self.assertEqual(list(get_overloads(impl)), overloads)
+
+ def some_other_func(): pass
+ overload(some_other_func)
+ other_overload = some_other_func
+ def some_other_func(): pass
+ self.assertEqual(list(get_overloads(some_other_func)), [other_overload])
+
+ # Make sure that after we clear all overloads, the registry is
+ # completely empty.
+ clear_overloads()
+ self.assertEqual(typing._overload_registry,{})
+ self.assertEqual(get_overloads(impl), [])
+
+ # Querying a function with no overloads shouldn't change the registry.
+ def the_only_one(): pass
+ self.assertEqual(get_overloads(the_only_one), [])
+ self.assertEqual(typing._overload_registry,{})
+
+ def test_overload_registry_repeated(self):
+ for _ in range(2):
+ impl, overloads = self.set_up_overloads()
+
+ self.assertEqual(list(get_overloads(impl)), overloads)
+
 
 # Definitions needed for features introduced in Python 3.6
 

Lib/typing.py

@@ -21,6 +21,7 @@
 
 from abc import abstractmethod, ABCMeta
 import collections
+from collections import defaultdict
 import collections.abc
 import contextlib
 import functools
@@ -121,9 +122,11 @@ def _idfunc(_, x):
  'assert_type',
  'assert_never',
  'cast',
+ 'clear_overloads',
  'final',
  'get_args',
  'get_origin',
+ 'get_overloads',
  'get_type_hints',
  'is_typeddict',
  'LiteralString',
@@ -2436,6 +2439,10 @@ def _overload_dummy(*args, **kwds):
  "by an implementation that is not @overload-ed.")
 
 
+#{module:{qualname:{firstlineno: func}}}
+_overload_registry = defaultdict(functools.partial(defaultdict, dict))
+
+
 def overload(func):
  """Decorator for overloaded functions/methods.
 
@@ -2461,10 +2468,37 @@ def utf8(value: bytes) -> bytes: ...
  def utf8(value: str) -> bytes: ...
  def utf8(value):
  # implementation goes here
+
+ The overloads for a function can be retrieved at runtime using the
+ get_overloads() function.
  """
+ # classmethod and staticmethod
+ f = getattr(func, "__func__", func)
+ try:
+ _overload_registry[f.__module__][f.__qualname__][f.__code__.co_firstlineno] = func
+ except AttributeError:
+ # Not a normal function; ignore.
+ pass
  return _overload_dummy
 
 
+def get_overloads(func):
+ """Return all defined overloads for *func* as a sequence."""
+ # classmethod and staticmethod
+ f = getattr(func, "__func__", func)
+ if f.__module__ not in _overload_registry:
+ return []
+ mod_dict = _overload_registry[f.__module__]
+ if f.__qualname__ not in mod_dict:
+ return []
+ return list(mod_dict[f.__qualname__].values())
+
+
+def clear_overloads():
+ """Clear all overloads in the registry."""
+ _overload_registry.clear()
+
+
 def final(f):
  """A decorator to indicate final methods and final classes.
 

Misc/NEWS.d/next/Library/2022-03-06-18-15-32.bpo-45100.B_lHu0.rst

@@ -0,0 +1,2 @@
+Add :func:`typing.get_overloads` and :func:`typing.clear_overloads`.
+Patch by Jelle Zijlstra.